Metal Loaded Epoxy, what metal is used in it?

[Ian PParticipant @ianp]

One of the materials I use occasionally is a metal loaded epoxy that is sold by RS Components as one of their ‘RS Pro’ range. I find it invaluable for creating this connector ‘shell’ for the 15 pole version of a micro USB that Sony call their Multiconnector on the A7 range of cameras. (see picture wired to 8 core cable)

As far as I can measure on the cured epoxy it has no electrical conductivity. The product Safety Data Sheet (11 detailed pages) gives some of its characteristics but makes no mention of conductivity.

Purely out of curiosity, I wonder what metal might be used. I’ve heard of ‘Rubber Loaded’ adhesive too)

Ian P

 

 

 

[Ian PParticipant @ianp]

This is the link to the RS catalogue page (which I forgot to include)

https://uk.rs-online.com/web/p/adhesives/0850962?gb=a

 

Ian P

[BazyleParticipant @bazyle]

I think some are metal loaded for strength and others for conductivity. We used products decades ago we called ‘DAG’ in both silver and gold versions. They were minute copper balls plated with either gold or silver in epoxy which were definitely conductive and space approved for use in satellites on circuits which had to stay conducting in the most extreme conditions.

[JasonBModerator @jasonb]

I use JBWeld and that contains about 10% iron but it is not a conductor.

I guess there is enough epoxy to cover all the iron particles so one does not touch the next so no electricity can flow.

[bernard towersParticipant @bernardtowers37738]

deleted, mine just says metal filler not what type

[Robert Atkinson 2Participant @robertatkinson2]

The “RS PRO ” range tends to be lower cost products. Data is somewhat lacking. Being a professional product consumer regulations don’t apply.
Unlike the “proper” metal filled epoxies like Devcon Araldite and JB weld which have a metallic content to give them strength, according to the datasheet and SDS this appears to have metal compounds as fillers. Primarily magnesium carbonate by the look of it. Also limestone (calcium carbonate) and talc.
Makes it fine for the OP’s application (basically thickened adhesive filler) but not for things you would use the various Devcon or JB products for. It seems similar to Plastic Padding (remember that?) which was stone dust filled polyester.

Robert.

[JasonBModerator @jasonb]

Isopon also did “Plastic Metal” which was grey, again due to the iron content.

[Robert Atkinson 2Participant @robertatkinson2]

Isopon still do a aluminium filled filler https://u-pol.com/product/isopon-fillers/isopon-alloy-wheel-filler/ It’s not explictly stated but probably polyester resin based tike their other fillers. Available from the usual outlets.

On the conductivity issue, most metal filled adhesives don’t have enough metallic content to provide conductivity. Any metal that forms insulating oxides on its surface is also a problem.
Conductive adhesives and paints are used in electronic applications. They are generally silver or nickel based. Silver has higher performance but is expensive. I specified some at work recently (842AR) and a 132ml can is over £250.

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

The “RS PRO ” range tends to be lower cost products. Data is somewhat lacking. Being a professional product consumer regulations don’t apply.
Unlike the “proper” metal filled epoxies like Devcon Araldite and JB weld which have a metallic content to give them strength, according to the datasheet and SDS this appears to have metal compounds as fillers. Primarily magnesium carbonate by the look of it. Also limestone (calcium carbonate) and talc.
Makes it fine for the OP’s application (basically thickened adhesive filler) but not for things you would use the various Devcon or JB products for. It seems similar to Plastic Padding (remember that?) which was stone dust filled polyester.

Robert.

I agree that generally the RS Pro is the lower cost products but this particular adhesive seems unique to RS and as far as I can tell is not a re-badged version of any other standard product. I was just curious why RS describe it as metal loaded but I suppose the magnesium carbonate is the metal content but its not metal as we know it Jim.

Regarding the other products you mention (Devcon, JB), how does the metal ingredient add strength?

I can see the added metal changing the properties of the cured product making it more machinable for example, but I am not sure how it would improve the adhesion to any substrate.

Ian P

[Ian P]

On Ian P Said:

I agree that generally the RS Pro is the lower cost products but this particular adhesive seems unique to RS and as far as I can tell is not a re-badged version of any other standard product. I was just curious why RS describe it as metal loaded but I suppose the magnesium carbonate is the metal content but its not metal as we know it Jim.

I suspect it’s the barium sulphate, but I can’t link to the specs page as the RS website is down at the moment.

Bill

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Way back in the 70s I was involved with making large press tools from filled epoxy resin. The filler was usually slate powder,or sharp sand. We also wanted to heat these in use and various metal powders were tried in the surface layers to put some volts through to obtain heat. None of the powders worked, for the reason no continuity was possible. We did get success with Aluminium flake though,due to flakes laying in contact with each other.

Keith

[Robert Atkinson 2Participant @robertatkinson2]

Ian P,

The metallic filler improves the cohesive strength and impact resistance of the adhesive rather than the adhesive strength. Filled adhesives tend not to be used for thin bondlines.

Robert.

[Nigel Graham 2Participant @nigelgraham2]

They might “tend not to be used” that way but ‘tend’ does not equal ‘never’ !

I have assembled laminated units using a low-viscosity ‘Araldite’ sold as two-part can packs, to which we added slate powder.

I can’t go into details but the method involved clamping a stack of plates in a jig fitted with a screw and thrust-block to compress the joints, so the bond-line would have been very thin.

The bulk of the glue that oozed out of the open front was carefully removed with a spatula then the remaining film removed with a brush and acetone, which dissolves uncured epoxy-resin. A spray-on parting material film on the steel jig prevented the work-piece sticking to it.

The acetone was also used for cleaning the mixer and other tools.

I can vouch for the strength of the joints, when trying to break up old test samples, with a big hammer. The adhesive and its bond rarely failed, but the laminae did.

[Michael GilliganParticipant @michaelgilligan61133]

For anyone with more than a casual interest in the subject, I would recommend keeping an eye out for this little book:

https://link.springer.com/book/10.1007/978-3-662-11032-4

I have the first edition, from when Bill Lees used it as the notes for a short-course that I was fortunate to attend.

First published in 1984, it is obviously not up-to-date, but it is very VERY informative.

Current pricing is high … but you never know when you might hit lucky [many books are being pulped these days]

MichaelG.

[egaParticipant @ega]

Another work which might be generally helpful is the design notes published some years ago by Ciba Geigy; I recall one issue called “Why Not Wood” about the Marcos wood framed car.

[Author]

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